1. Field
The present application relates to an evaluation apparatus of fluorescent object population, an evaluation method of fluorescent object population and a computer readable storage medium for evaluating a fluorescent object population such as a fluorescence-stained cell population.
2. Description of the Related Art
Conventionally, there has been known an evaluation apparatus of cell population (flow cytometer) in which a solution containing fluorescence-stained cell population is let to flow through a light-transmitting tube, a time change in a light emission amount of fluorescence is measured while irradiating excitation light to the tube, and statistical data regarding the fluorescence of the cell population is obtained based on the time change (Japanese Unexamined Patent Application Publication No. H 9-145593).
In recent years, there has been proposed an evaluation apparatus of cell population (hereinafter, called as “image cytometer”) in which, instead of letting the solution containing cell population flow through the tube, a fluorescence microscope image of the cell population is obtained, and by performing image processing on the fluorescence microscope image, statistical data similar to the above data is obtained (Japanese Unexamined Patent Application Publication No. 2006-194711).
With the use of the image cytometer, there is no need to go through complicated measuring steps, and further, even detailed data regarding a structure in the cell can be obtained, which provides high availability.
However, a lot of noises are generated in the fluorescence microscope image, so that in the image cytometer, there is a need to distinguish between a cellular image and the noise, and to remove the latter before obtaining the statistical data. Actually, in the image cytometer disclosed in Japanese Unexamined Patent Application Publication No. 2006-194711, a bright spot whose brightness value exceeds a threshold value in the fluorescence microscope image is regarded as the cellular image, and a bright spot whose brightness value is equal to or less than the threshold value in the image is regarded as the noise, and the latter is removed.
However, the degree of staining of the individual cells varies, so that a fluorescence intensity is lowered depending on the cell, and the intensity sometimes becomes almost equal to a background level (noise level). Since such a cellular image is removed as the noise, an error occurs in the statistical data.
Note that if the threshold value is set low, a possibility of accidentally removing the cellular image is decreased, but, instead of this, there is increasing a possibility that a lot of noises remain, so that it is not possible to securely reduce the error in the statistical data.